Permute an MPS or MPO

[hanfluid]

Hello,

I'm wondering if there is any function for permuting an MPS or MPO withouth converting to full tensors?

Thanks for your help!

[dolgov]

In general, no, since the TT ranks may become full anyway:

>> I = eye(64);
>> I = reshape(I, [8 8 8 8]);
>> tt_tensor(I)
ans is a 4-dimensional TT-tensor, ranks and mode sizes: 
r(1)=1 	 n(1)=8 
r(2)=8 	 n(2)=8 
r(3)=64 	 n(3)=8 
r(4)=8 	 n(4)=8 
r(5)=1 
>> I = permute(I, [1 3 2 4]);
>> tt_tensor(I)
ans is a 4-dimensional TT-tensor, ranks and mode sizes: 
r(1)=1 	 n(1)=8 
r(2)=8 	 n(2)=8 
r(3)=1 	 n(3)=8 
r(4)=8 	 n(4)=8 
r(5)=1 

However, if the tensor admits sequential permutations without significant change of ranks, core/move_tt_block.m may help.